Use Lower Grade Oil???

[geoffro1212]

I have 60b's in my bertram as well and was told if the they stop producing black smoke at startup or when chaseing a fish there was somrthing wrong. (quoted from a volvo mechanic) PS - I use 15/40w castrol oil and they have over 3500 hour on them and untouched

[Fatenhappy]

Just sitting on the side lines,

Just like to say thanks to FNQ, Cormorant and a few others for a really interesting thread .....

Just like to ask FNQ, as I think it was you that mentioned, why leave the likes of Valvoline on the scrap heap as obviously you know far more on this subject than I do ?

[NEWBY]

Interesting that this has resurfaced as I have done a few hours since starting this thread.
Tanks have been ammonia bathed to kill off bug.
ALL traces of previous fuel additive have been erased.
FUELTREAT is now the only additive used.
The lower grade mono 40 oil is being used now.
RESULTS.......
No more smoke even after prolonged trolling for 3 or 4 hours.
No more soot at all.
Boat running perfectly...
25-30 hours running and the oil is still nice and clean...

All the comments and suggestions here have made for a fascinating debate among the oil suppliers and their associated laboratories. I will keep you all posted with any information they supply me with.
Once again, thanks for all your input and keeping this thread friendly.